Blank-holder press



u y 8, J. A. MULLER 2,354,041

BLANKHOLDER PRESS Filed April 1, 1942 2 Sheets-Sheet 1 BY Warm ATTORN EYS v i July18, 1944- A. MULLER 2,354,041

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BY 7M 7M RNEYS Patented July 18, 1944 Johan A. Muller, Dayton, Ohio, assignor to The Hydraulic Development Corporation, Inc., Wilmington, Del., a corporation of Delaware Application. April 1, 1942, Serial No. 437,303

' a 11 Claims.

This invention relates to presses and, in particular, to hydraulic presses having blankholding arrangements in association with drawing devices.

In certain presses of this type in which the clamping force is created by relative movement of the press ram and blankholder platen, the clamping cylinder piston arrangement is provided with means for partiallybalancing forces created in the balancing cylinders so that a ma terially smaller force is to be derived from the press ram to create the desired clamping action.

Such presses, as heretofore known and disclosed, for instance in Figure 3 of the U. S. Patent No. 2,167,941 to Ernst, require for each clamping cylinder piston arrangement a first cylinder in the press platen, a second cylinder in the press head, andtwo plungers respectively reciprocable in the said two cylinders and connected with the press platen and the blankholder platen.

It is an object of this invention to provide an improved blankholder press which will be ma terial iy simpler in construction and cheaper in manufacture than the presses referred to in the preceding paragraph, without, however, sacrificing the advantages of the latter. v

It is another object of the invention to provide a blankholder press having means associated with a blankholder'cylinder piston arrangement for partially balancing forces created therein, 30

in which only one clamping cylinder for each clamping cylinder piston arrangement is required.

It is a further object to provide a blankholder press, in which each blankholder cylinder piston arrangement comprises a plurality of hollow clamping pistons.

It is a still, further object to provide a blankholder press, in which each blankholder cylinder piston arrangement comprises two plungers extending into one and the same clamping cylinder, which latter is movable relative to said plungers. i

It is another object of the invention to provide a blankholder press asset forth-in the preceding paragraph, in which the plungers are fabricated of seamless steel tubing.

Still another object of the invention consists in the provision of a blankholder press having each clamping cylinder piston arrangement provided with two clamping pistons, in which the total height of the press is materially reduced over that of similar presses heretofore known.

These and other objects and advantages of the invention will appear more clearly from the I01- lowing specification in. connection with the accompanying drawings, in which: t

Figure 1 diagrammatically illustrates a blankholder press according to the invention. a Figure 2 shows a-single clamping cylinder piston arrangement in idle position.

Figure 3 is a view similar to Figure 2, but showing said clamping cylinder piston arrangement Just prior to the actual clamping action.

Figure 4 shows the arrangement of Figures 2 and 3 in clamping action.

Figure 5 illustrates the first stage of the retraction stroke of the clamping cylinder piston arrangement.

Figure 6 shows the second stage of the retraction stroke of the arrangement of Figures 2 to 5.

Figure 7 diagrammatically illustrates the distribution of forces during the actual clamping action.

Genet'al arrangement The blankholder press of the present invention is characterized primarily by an improvedfand simplified clamping arrangement, according to which only one cylinder is' provided for each clamping cylinder piston arrangement.

The arrangement is such that two plungers, one of which is stationary, while the other is connected to the blankholder platen, extend into one and the same clamping cylinder, which latter I movable relative to both plungers and actuated "by the press ram.

Structural arrangement Referring now to the drawings in detail and to Figure 1 thereof in particular, the press structure shown therein comprises a press head Ill having a press cylinder il in which is reciprocably mounted a press ram l2.

0 The press ram I! has connected thereto a press platen is which, in its turn, carries a punch I4 adapted to pass through a bore ii in a blankholder; platen L6 in order to shape a work piece which is held by the blankholder platen I6 during the drawing or shaping action. The blankholder it has connected thereto a plurality of holding members ll which extend through bores il in the press platen i3 and have their upper ends provided with a thread I 9 adapted to receive a nut 20. As will be seen from the drawings, the

adjustment of the nut 20 varies the maximum distance between the bottom portion of the press platen l3 and the adjacent face of the blankholder platen l6.

u Adiustably mounted in each of the supporting members H is a threaded rod 2| adapted to engage the head I for stripping the work piece from the punch I4. The blankholder platen l6 carries a plurality of hollow plungers 22 which extend into the clamping cylinders 23. supported by and connected to the press platen IS in any desired manner. The clamping cylinders 23 extend into correspondingly shaped recesses 24 provided in the press head It).

Connected to the press head I 0, for instance by fitting members 25 and screws 26, are hollow plungers 21 extending into the respective cylinders 23, and also adapted to telescope into the hollow plungers 22. It should be noted that the outer diameter or the plungers 21 and the inner diameter of the plungers 22 are so dimensioned that when these plungers are telescoped in each other, there is a marginal area between the outer surface of the plunger 21 and the adjacent inner wall surface of the plunger 22, which will allow fluid to escape from the plunger 22 into the cylinder 23.

The hollow plungers 22 and 21 may, if desired, be manufactured of seamless tubing, which materially facilitates the production of the press and reduces the cost of production, inasmuch as no particular machining operation is required.

The interior of the plungers 21 communicates through bores 28 in the fitting members25 with a conduit 29 comprising check valves 30 and having branch conduits 3| with check valves 32. The conduit 29 communicates through a conduit 33 with a control valve, generally designated 34. The control valve 34 has an opening 35 continuously establishing communication between a cylinder bore 36 and a fluid tank or reservoir 31 mounted on top of the press head i0. Reciprocably mounted in the cylinder bore 36 is a valve member 31 with two spaced pistons 39, 40, for selectively establishing or preventing communication between the Opening 35 and the opening, 4|, which latter communicates with the conduit 33.

The piston 39 is adapted to be acted upon by pressure fluid conveyed through a conduit 42, whereas the piston 40 is adapted to be actuated by pressure fluid conveyed through the conduit 43. The conduit 42 communicates with'a conduit 44 having one end connected to the upper portion of the press cylinder while the other end leads to a four-way valve 45 of any standard design, which may be operated manually by actuation of the lever 45.

The four-way valve 45 has furthermore connected thereto a conduit 41 leading to the fluid tank 31 and a conduit 48 communicating with the conduit 43 and leading to a passageway 49 which, in its turn, is connected to the lower portion of the press cylinder. The valve 45 has connected thereto a further conduit 50 which communicates with the pressure side of a constant delivery pump 5| of any desired type. The suction side of the pump 5| communicates through a conduit'52 with the tank 31.

Branching oil from the conduit 29 and respectivel associated with the clamping cylinders 23 are conduits 53 with pressure relief valves 54, which are preferably individually adjustable so as to enable different clamping pressures in each of the clamping cylinders.

Operation It may be assumed that all parts of the press occupy the position shown in Figure 1, and that it is now desired to carry out a working cycl of 75 the press. To this end, the operator starts the pump 5| and actuates the valve 45 by operation of the lever 46, so that fluid connection is established between the conduits 44 and 50, while the conduits 41 and 43 ar brought into fluid connection with each other. Pressure fluid from th pump 5| is then conveyed through valve 45 and conduit 44 into the upper portion of the press cylinder A part of the pressure fluid in conduit 44 passes through conduit 42 and acts upon the piston 39 so as to shift the valve member 38 toward its right hand or closing position, in which fluid connection is interrupted between the conduit 33 and the opening 35. Furthermore, fluid is withdrawn from the lower portion of the press cylinder through the passageway 49, conduit 48' and valve 45, and is exhausted into the tank 31. The press ram i2 then moves downwardly as fast as fluid is expelled from the lower portion of the press cylinder While the ram |2 moves downwardly, the press platen I3 and the clamping platen I9, suspended thereon by means of the members l1 and nuts 20, move downwardly in unison. During this downward movement, the space between the lower ends of the plungers 22 and the lower ends of the respective plungers 21 increases, thereby creating a suction effect, which causes the check valves 32 to open so that fluid from the tank 31 passes through the check valves 32 and conduits 29 into the respective plungers 21.

As soon as the blankholder platen l6 engages the work piece, it comes to a halt, at which time the clamping cylinder piston arrangement occupies the position shown in Figure 3. The press platen 3, however, continues its downward movement; Due to the downward movement of the press platen l3 and the cylinders 22 connected thereto, relative to the pistons 22, the latter telescope into the cylinders 23, as shown in Figure 4, and cause the creation of clamping pressure, When this pressure exceeds a predetermined value, for which the pressure relief valves 54 have been set, the excessive pressure is relieved through the said relief valves into the tank 31. The press ram |2 and, therefore, also the press platen |3 continue their downward movement so as to cause the punch H to shap the work piece to be drawn.

It should be noted that, although the clamping plungers 22 havea relatively large area for effecting the desired clamping of the work piece, only a relatively small clamping force has to be derived from the press ram |2, since a portion of the forces acting in the clamping cylinders is balanced.

The actual distribution of the forces acting in the clamping cylinders will be best understood from a reference to Figure 7 which, in a simplified form, illustrates a clamping cylinder 23 with the clamping plungers 22 and 21 pertaining thereto.

Assuming that the cylinder 23 is moving downwardly, it.will be clear that pressure is created in the cylinder 23, since the space filled by the plunger 22 telescoping into the cylinder 23 is larger than the space freed by the lower portion of the plunger 21. Consequently, the forces in the cylinder 23 are composed of the forces acting upon the bottom a and rim b of the plunger 21, the forces acting upon the bottom 0 and rim d of the plunger 22 and the forces acting upon the bottom e and top f of the cylinder 23.

The forces acting upon the bottom a and the rim b of the plunger 21 are counterbalanced by thetank 31 through "the checkjvalves l2 and ffifh wa acting bath bout-1h and top tar-j tlglnsiof the cylinder 2;, the area oifwhich eduals balance each other, as will tbe obvious from the drawing..- jcpnsequentiy, only. ;the forces acting, on the bottomlportion of the plunger n which portion equals, I i p t.

-- V (gridir- T' T r is unbalanced, and this vforce is the "only force to bederivfed' from th ram or to be detracted from'th'e force acting upon the ramfor malnf" tai'n'lngfa me iakh a tive ly high clamping-pressure is created by the pre s faccording to the invention, w ammy a small portions of this clamping pressure is; d e-f rived from the press ram if] Whenflth drawing orshaping'action hasbeen completed by the punch 14, the operatorrever'ses' the position of the valve 45; thereby establishing? fluid connection be'tweenjtheconduits ll and ll,

determined clamping pressure onf p sif indrror' g; it two pressing plungers 15 needs 7 am whil simultaneously connecting the conduits n it sa 'h some:

1 Pressure Lfiuldis 'th enj delivered by the pump 6| through conduit 5ll'and valve into the con-' duit 4 8, From, her a part of the 'pres'sure fluld isconveyed through conduit 43 to thepiston ll, soas tofshift the valve member 38 into the position shown in Figure 1; in which .fluld connection is established between the conduit II and the opening"! Pressure fluidintheconduit fl' flows through thepassagewaylsintofthe lower portion of the press cylinder l l" and startsthe upward or'retr'actionmovement of the ram l2. g "when th rarn l2 and; thereforefthe press platen it connected thereto, move upwardly the fluid expelled from the upper portionof the press cylihderl Fescapesthrough the conduits i and llilinltbthe'tank' 31. Due to the upward'mo'vemer t of t 'epress platen 13', a'relative withdrawal of the clamping plunger 22 1mm the clamping cylinder 23 1s effected and, since the efiecti'vearea oi the plunger 22' is larger than the eflective area I of theplunger 21; a suction effect is created in" thecylln'der'll,which causes fluid toflow from plungers Zlihtofthe cylinders 23. Consequently the blank-holder platen i6 remains in its i lower position, while the distance between -the press" platenJ; and the blankholder platen l8 increases. This actlon is shown in Figure 5.

If, during the upward movement of the press platen IS, the work piece should stick to the punch H, the blankholder'platen It will move upwardly together with the press platen l3, so that there will be a space between the upper face of the press platen and the bottom face of the nuts 20. When the knockout rods 2| then engage the press head l0, they will prevent further upward movement of the blankholder platen i8, while the press platen i3 continues its upward movement and, in this way, will strip the work piece on the punch ll so, that the work piece may be removed.

At the end of the first stage of the retraction stroke of the press platen ii, the latter abuts through the conduits 28 and and bor V startja newgcyicle .1. ,lniatrially decreases'i the total'fl eig not telescope into themunge'rizz; in w h .isjmerely to-exchange the plunger s thenuts 2Q andp-iurther upward movement-of" the 'pre'ss platen il causes the ilafitgw and I the blankholder laten IE to moveupwardly in irm-s song 'ihis initiates 'thesecond stage of the, retraction strokef,las indicated in FigurefiJnswhi ch; a relative approaching movement 'lseflectedi be; tween: the plunger's zz'and 21. This causes. fluid. to expelled from th-cylindersjii; and to new,

and into .the tank .3]. V

e. press ram i of its retractionlstroke the the pump u; remove-the was; i

;.Aswill be clear, r in, edrawmgs tr ture according to. the intention constitutes a material simplification-over the stri'ict'ur for;

ilarj. presses 'heretoiFpre {knownmg cylinder 'isf required irijthe pres head; not only savestinatjerial an .ork thejreby ing"u ithe produqtionfof Such Dre es fAlthQugh.. as m ntioned abov to 'make both plunge stance .the plunger 22 "aywbe s "lid witiho very simple mannergtojncreas 7 press. J All that is necessary in ,su

plunger-s. fIfhis"is 'anothfir materi over. similar presses heretofore know such a 'p urpos ,e, required not only e ongat plunger s,bli t alsojriew cylinde f It. willhe understood thatcIgdesir prehend within iny invention such in as com within the scope or the clai inventiong i i .7 1'. If Having t us' fully described my inventiomwhat' v .I claim as newfand-desireto' securehy I ette'ris, v

Patent, is:

1. In combination ina pies; exertlng pressure one work' piece; blankhold'er'f means for holding said w'ork fpiece "while it y is being shaped, and a plurality of clamping cyl;

rs 'q m e v mt v lv so net-ed. th' m new bl nkh'o si me s we. exerting pressuremnth latter in 'resporise'toa'g reianvemdvement -of said ram and said 1 movable by said ram, and also comprising two hollow plungers extending into said cylinder and adapted to be telescoped into each other, one of said plungers being stationary and forming fluid passage means communicating with the interior of said cylinder, while the other and larger plunger is connected to said blankholder means.

2. In combination in a press, a reciprocable press ram for exerting pressure on a work piece to shape the same, blankholder means for holding said work piece while it is being shaped, a plurality of clamping cylinders arranged to move in unison with said ram, a plurality of first plungers stationarily arranged and respectively extending into one end of said clamping cylreached the end .inders, and ,a plurality of second plungers' con- :necteid'l to: saidsblanlrholder means so as .to move in unison therewith and respectively extending -tinto the otherzend,. of said cylinders, said-second plungers having adiameter larger than said first plungersand" being': adaptedin response to.

relative movement :of said ram --1towards said blankholder means to createclamping pressure in said clamping, cylinders] and to convey said clamping pressure to. said blanlrholder means.

.3, .I-n combination in .a 3 press, a ;pres s ahead,

:press ,ram zreciprocable ,in :saidhead for exerting shapingpressure on a work :piece;,1b1ankholder means for holding said gwork' -piec e-while;it is 'being shaped, saidpness ram'beingimovable .rela- 1 tive' to said blankholder means, ;a. plurality of clamping cyiinders connected to and movable in ;unison. with said ram and adapted-to extend .into a recess in said :head, at lurality of station- ;ary;.plungers supported by ssaid. head and respectively extending into said cylinder, and a plurality of additional -clamping 'plungershaving a diameter larger than sald'statiOnary plungers andsbeing connected to saidfblankholder means, said -.additional plungers being adapted in c ooperation with said cylinders-and in response to relative movement of-saidpress ram and said blankholder means to create clampi g pressure :in said clamping cylinders and to convey said pressure to said blankholder means.

kin-combination in .a press, a reciprocable press platen, blankholder means connected with jbutrnovable relativeto saidpl'aten forholding .a workpiece while itsisbeing shaped, a pluralityof clamping cylinders supported ;by and movable withsaidnlaten, azplurality ofstationary plungers respectively extending into said cylinders and forming conduitmeans communicating with the 'interiorof :said cylinder, a plurality of additional plun'gers operatively connected toand movable ,inunison with said .-blankholder means and respectively extending into said cylinders, said additionslkplungers'having a largerdiameter than said stationary 'plungers and being adapted in response to ;a relative movement of said platen towardssaid blankholdenmeans .to create clampingpressure in said clamping cylinders and to convey saidpressureto said blankholder means.

5. In combination in a press, reciprocable pressinganeans for shaping a workpiece, blankholder means movable relative -to said pressing meansfor holding said workpiece while it is being shaped, and a-plurality of clamping cylinderpiston-assemblies operatively connected with said pressing means and said blankhold'er means and operable-in response to-a relative movement of said-pressing means and said blankhoider means "for creatingand exerting clamping pressure on the latter, each of said clamping cylinder-pistom.

assemblies ,comprisingone cylin'derand two cooperating pmnsers, one of which. is stationary,

while theother is rr'iovable in unison with saidblankholdergm'eans.

-6. Ins press, a press framers press platen {or exerting working pressure on .a work piece, .a

vblankholder means for holding said work niece,

plunger means, stationary with said, frame,

plunger means stationary with said iblan kholdsr means,'and cylinder means stationary with said platen and reciprocable over said ,plunger means.

7. In a press, a .press head, apress platen. a

=blankholder'connected =to.-and mvva'ble relative-xw said platen, first plunger means=stationary-reltive to said press headysecond plungerwmennsstationary relative to said .blankholden meanm l and cylinder means stationary .relative to platen and reciprocable over said first. sndseoond plunger means. v i

8. In apress, apress head, a.pressplaten ciprocable relative to .said head, blankholdorf 'meansreciprocable relative -to said'headi and platen, plunger means stationary relative {to ,sa'idl' head, 1 plunger means -stationa r yrelatiye to 1 blankhulder, (and cylinder means .reciprocsble over both of said plunger mesnslandfgsjtstlonary relative'to-saidplaten. 9. In a-double actingpresaapress heads ported by and movable relative to ,saidIplaten; cylinder means stationary relative tofl said'pla'ten.

.flrst. plunger means stationary re,lative to head and extending intoone end of said cylindor,

second plunger means stationary relative Jinnah! blanlcholder and extending into the other end ,0! said cylinder. 'j J 10. In a press, a press-hesd,.a:press-platenwreciprocable relative to said -head, blankhol'dormeans connected with and movablepelative to.

said platen, cylinder meanslcarribdbysaid platen,

plunger means stationary relative to .I

and extending into said cylindernienna'secondf plunger means stationaryrelative mmam p holder ,means and extending into said-cylinder... said lastlmentioned plunger meansbeing hollow and adapted to telescope with-said first. plunger means.

11. In :a press, a press head, .a press ciprocable relative to said head, blankholden,

means associated with said ram-and. movable-relativethereto, cylinder meansassociatedwith-said. 1

ram and reciprocable therewith, .a gilrst plungermeans stationary relative tosaid -head and extending into said cylinder meanssecondplungermeans stationary relative to said-blankholder and; extending into said cylinder means and adaptedin response to relative movement ,between said. I blankholder and said press ram to generatepressure within saidcylinden. 

